1. Field of the Invention
The present invention relates to a photographing apparatus and a photographing method for obtaining an image through photographing, and a computer-readable recording medium containing a program for causing a computer to carry out the photographing method.
2. Description of the Related Art
In an image pickup device, such as a CCD, used in digital cameras, dark current is generated when the image pickup device receives no light. The dark current is generated due to electron-hole pairs generated by thermal excitation of the semiconductor, and appears as noise in pixel values outputted from the image pickup device. In order to address this problem, various techniques for correcting for the dark current noise have been proposed.
For example, a technique has been proposed, in which, before or after a subject is photographed, a light-shielded image is obtained by carrying out photographing for the same length of time as the exposure time of the photographing of the subject in a state where the image pickup device is shielded from light, and image data of the light-shielded image is subtracted from image data of the image obtained by photographing the subject, thereby achieving correction for the dark current noise.
In a case where the light-shielded image is obtained in this manner, an approach has been proposed, in which the fact that the light-shielded image is being taken is informed to the photographer by displaying an indication of the fact on the monitor of a digital camera (see Japanese Unexamined Patent Publication No. 2000-224532). In another proposed approach, a shutter releasing operation is inhibited while the light-shielded image is taken (see Japanese Unexamined Patent Publication No. 2000-236477). In yet another proposed approach, if the shutter releasing operation is made when the light-shielded image is being taken, priority is given to the releasing operation and the light-shielded image is taken anew after the photographing has been finished (see U.S. Pat. No. 6,710,807). In further another proposed approach, timing for taking the light-shielded image, i.e., whether the light-shielded image is taken before or after the photographing, is set for each photographing mode of the digital camera (see Japanese Unexamined Patent Publication No. 2000-184269).
However, in the approach where the releasing operation is inhibited, the user may not carry out photographing at the moment he or she wants and may miss the right moment for releasing the shutter. In the approach described in Japanese Unexamined Patent Publication No. 2000-184269, the user can release the shutter at any moment he or she wants, however, if the exposure time and/or the sensitivity of the first photographing differ from those of the second photographing, the light-shielded image taken after the second photographing may not be appropriate for correcting the image taken in the first photographing.